removing head from character mesh using another head mesh
I think your best solution is brute vertex editing. Delete the head you want to get rid of by circle selecting the vertices and creating as smooth a transition as possible. In edit mode (of the body) you can even place the new head exactly where you want it. You can then refine the vertices and begin stitching them together.
A more complicated, but possibly faster, way would be to isolate the neck loop on the replacement head, separate it from the new head, convert it from a mesh into a curve, place it exactly above the body where you're going to be putting it (having already mostly removed the old head, and then using &quot;Knife Project&quot; to cut new geometry around the neck hole. You'll still have issues marrying the heights of the different vertices, which you'll have to do by hand, but it should be pretty closely aligned.
Good luck!
Hi, to follow up: You select the ring of vertices, hit [shift]+[D], then [P] to separate them from the new head object. Choose &quot;by selected.&quot; Then click off. Select the ring of vertices that you've separated and go to OBJECT&gt;CONVERT TO&gt;CURVE
You will be left with a curve, which you can then use for knife project.